diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index a0f53713b0..ceb92c9cb6 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -7319,6 +7319,17 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
      #TMPDIR = "${TOPDIR}/tmp"
                     </literallayout>
                 </para>
+
+                <para>
+                    The filesystem used by <filename>TMPDIR</filename> must
+                    have standard filesystem semantics (i.e. mixed-case files
+                    are unique, POSIX file locking, and persistent inodes).
+                    Due to various issues with NFS and bugs in some
+                    implementations, NFS does not meet this minimum
+                    requirement.
+                    Consequently, <filename>TMPDIR</filename> cannot be on
+                    NFS.
+                </para>
             </glossdef>
         </glossentry>